The magnetic properties and recording characteristics of (Dy,Tb)FeCo films are dependent upon the anisotropy dispersion of rare earth constituents and the exchange integral between rare earth and transition metal sub networks. The exchange coupling coefficient &lgr; and the domain wall mobility&mgr;effare found to be interrelated by both measurements and calculations. The higher the &lgr; or the lower the&mgr;eff,the higher bias field that is required for magneto-optical recording. The temperature independent &lgr; is demonstrated to be an important parameter in the assessment of magnetic properties and recording characteristics of sperimagnetic films. ©1997 American Institute of Physics.